Precursory Signals (SST and Soil Moisture) of Summer Surface Temperature Anomalies over the Tibetan Plateau

Huimei Wang,Sai Wang,Ge Liu,Kejun He

doi:10.3390/atmos12020146

Abstract

Understanding the variability of surface air temperature (SAT) over the Tibetan Plateau (TP) and its precursory signals is of great benefit to climate change adaptation and socioeconomic development. This study explores the precursory signals of summer SATs over the TP in oceanic and land boundary conditions. The results show that the summer eastern TP SAT is significantly correlated with three precursors in April: the high-latitude North Atlantic sea surface temperature (SST), the northern Indian Ocean SST, and the Indian soil moisture (SM). The April SST anomalies (SSTAs) in the high-latitude North Atlantic can exert a cross-season impact on the summer SAT over the TP through two processes. The SSTAs in the high-latitude North Atlantic maintain from April to summer and modulate atmospheric circulation over the eastern TP through exciting a downstream wave train during summer, and finally modulate the summer SAT over the eastern TP. In addition to the above process, the April SSTAs in the high-latitude North Atlantic may remotely regulate simultaneous SM in the Indian subcontinent through stimulating a downstream wave train pattern. Through a persistent SM–precipitation interaction, the April Indian SM anomaly can affect the local precipitation and associated condensation heating anomalies during the ensuing summer, which forces an anomalous cyclone–anticyclone pattern around the TP and accordingly affects the summer SAT over the eastern TP. Additionally, the SSTAs in the northern Indian Ocean can persist from April to summer and adjust the intensity and location of the western North Pacific subtropical high through the Kelvin-wave-induced Ekman divergence during summer, eventually affecting the summer eastern TP SAT. The three precursory signals, which synergistically contribute to the variability of the summer eastern TP SAT, can be applied in predicting the summer SAT over the eastern TP.

Highlights

The Tibetan Plateau (TP), situated in subtropical eastern Eurasia, is the highest plateau in the world
Wang et al [22] suggested that the SST anomalies (SSTAs) and its coupled surface air temperature (SAT) anomalies in the Atlantic Ocean can persist from the preceding winter to ensuing summer, stimulate a zonal wave train extending from the Atlantic to Eurasia, and eventually cause atmospheric circulation and associated SAT anomalies over eastern China
The leading empirical orthogonal function (EOF) mode (EOF1), which accounts for 37% of the total variance, shows a homogenous variation over almost the whole TP, except for several scattered opposite-sign SAT anomalies appearing along the southern flank of the TP

Summary

Introduction

The Tibetan Plateau (TP), situated in subtropical eastern Eurasia, is the highest plateau in the world. Sea surface temperature anomalies (SSTAs) in several key ocean areas are the important factors affecting the variability of the SAT over the TP. Wang et al [22] suggested that the SSTA and its coupled SAT anomalies in the Atlantic Ocean can persist from the preceding winter to ensuing summer, stimulate a zonal wave train extending from the Atlantic to Eurasia, and eventually cause atmospheric circulation and associated SAT anomalies over eastern China. The precursory signals, which are responsible for the summer SAT anomalies over the TP, are explored in oceanic and land boundary conditions, especially, in the Atlantic and Indian Oceans and the Indian subcontinent

Data and Methods

Results

The Effect of SSTAs in the High-Latitude North Atlantic

Joint Effect of Three Precursory Signals